A number of scissors and shears have been proposed with interchangeable blades, with several motivations for providing interchangeable blades, including reducing manufacturing costs by forming the handles from a relatively inexpensive, somewhat softer material than the blades, which are desirably formed from a harder material, such as steel, that can provide a sharp and relatively durable edge.
Many lawn and garden cutting implements have been proposed with interchangeable blades have two blades sandwiched between extensions of the handles, with a pivot bolt passing through the first handle extension, first blade, second blade, and second handle extension. A nut adjacent the outer surface of the second handle extension is threadably engaged with the shank of the bolt to hold the handles and blades together. Because the pivot bolt/nut assembly passes through multiple metal plates (for example, ends of the two handles and two blades), the thickness of the cutting implements through the pivot bolt and nut is significantly greater than the thickness through the pivot bolt of conventional shears, where the bolt only passes through two metal plates. The increased thickness displaces the plane along which the blades meet away from the outermost points of the pivot bolt and nuts, increasing the thickness of the cutting portion of the shears so they cannot cut twigs and branches close obstructing parts of a plant. Such obstructing parts may be the main stems or side branches of the plant.
Another disadvantage of many known garden shears with interchangeable blades is that tools are required to remove and replace blades. For example, screwdrivers, Allen keys, or wrenches must be used with either the bolt, the nut, or both.
Shears have been patented that at least apparently do not need tools for dissasembly and reassembly of the handles and blades.                U.S. Pat. No. 4,56,656 to Wallace et al. describes shears where a coin or other bladed implement is needed to remove the bolt.        U.S. Pat. No. 4,980,975 to Hodson describes secateurs with a screw head on one side of the pivot area. The screw head has a rib that extends outward and can be gripped by a user's fingers. The rib must extend outward a significant distance to allow sufficient grip to tighten the screw to the bolt and remove a tightened screw from the bolt.        U.S. Pat. No. D422,856 and D426,755 to Wu describe anvil and bypass pruners, respectively. There is a knurled knob that may be either the head of a bolt or a nut on one side of the pivot area and a corresponding nut or bolt head on the other side of the pivot area.        U.S. Pat. No. D459,168 S describes shears having a feature with a modified triangular shape that could be a washer or a part of a nut or bolt.All of these have structures that protrude outward on both sides of the pivot area, increasing the distance between the outermost point of the pivot and the plane along which the blades cut. Further, the Wallace et al. and Hodson shears have numerous small internal parts, complicating the processes of disassembly and reassembly.        
It would be desirable to provide cutting implements with interchangeable blades that can be interchanged without the need for any tools and with a minimal number of parts to be disassembled and reassembled when the blades are changed. It would also be desirable to provide garden shears, including hedge shears, grass shears, loppers, and pruners, with a narrower fulcrum than previous garden shears with interchangeable blades, such that the cutting plane is close to the outermost surface of the fulcrum area. It would also be desirable to provide a pruning saw with an interchangeable blade that can be replaced easily and safely without tools.